Rotary impact tool



July 5, 1966 KESSLER ETAL 3,259,025

ROTARY IMPACT TOOL Filed Feb. 3, lQ-l 2 Sheets-Sheet l July 5, 1966 L, KESSLER ETAL l 3,259,025

ROTARY IMPACT TOOL 2 Sheets-Sheet 2 Filed Feb. 1964 United States Patent Office 3,259,025 Patented July 5, 1966 F y 12 Claims. (Cl. 91-1) The present invention relates to rotary impact tools in general, and more particularly to an impact tool of the type having means for yautomatically arresting the motor which imparts torque to a wrench, screwdriver or another implement coming in direct engagement with a bolt, screw, nut or the like.

It is well known to utilize portable impact tools for installing or removing nuts, screws or bolts. Such impact tools are equipped with motors which rotate an yanvil serving as a means for supporting a wrench or a screwdriver and for imparting thereto a torque necessary to install or to loosen a screw, bolt, nut or the like. It is also known to provide such tools with devices which automatically arrest the motor after a predetrmined interval of time or in response to a predetrmined resistance which bolt or nut offers to further rotation of the anvil. It was found that such control devices cannot always insure satisfactory application or loosening of nuts or bolts because the member of revolutions which the motor performs in a given period of time varies in dependency on many factors and because the resistance of a nut or bolt to further rotation is not an accurate indicator that the nut or bolt is driven home all the way.

Accordingly, it is an important object of my invention to provide an improved rotary impact tool which is constructed and assembled in such a way that the control device which actually arrests the motor operates in dependency on factors other than time and/or resistance to rotation in order to insure that the tool may apply a bolt or a nut with requisite force independently of the rotational speed of the motor.

Another important object of the invention is to provide a control device which is constructed and assembled in such a way that a series of screws, bolts or nuts may be applied with a force whose magnitude varies within 'a narrow range to insure that each screw, bolt or nut takes up an equal share of stresses.

A further object of our invention is to provide a rotary impact tool which is constructed and assembled in such a way that the operator is automatically warned when the motor is arrested to make sure that the operator can start the next installing or removing operation without undue delay.

An additional object of the invention is to provide a novel control device for the motor or a rotary impact tool, particularly for an impact tool which is provided with a pneumatic motor, and to construct the control device in such a way that it arrests the motor simultaneously with actuation of the signal generating device.

A further object of the invention is to provide a control device which may be readily adjusted to arrest the motor after 4a selected number of revolutions so that the impact tool may be used for application or removal of screws, bolts and nuts with a force which is commensurate with the requirements in a given operation.

Still another object of the invention is to provide a control device which automatically returns to its-starting position as soon as the operator is made aware of the fact that the motor of the impact tool is arrested.

A concomitant object of the invention is to provide novel control valve and a novel counter mechanism which may be utilized in a pneumatic rotary impact tool of the above outlined characteristics.

With the above objects in view, one feature of our invention resides in the provision of a rotary impact tool which comprises a rotary motor, arresting means operative to arrest the motor, and a counter mechanism operatively connected with the motor and arranged to operate the arresting means after the motor completes a predetermined number of revolutions. In other words, rather than relying on time or on the resistance which the anvil of the impact tool encounters in installing or removing -a screw, nut or bolt, we rely on a counter mechanism which is adjustable and which arrests the motor after a preselected number of revolutions.

If the impact tool of our invention is equipped with a pneumatic motor, the arresting means preferably comprises a suitable shutoff valve which is installed in the channel means connecting the intake of the motor with a source of compressed gas, and the counter mechanism may comprise a spindle or a similar control member which is movable in response to rotation of the motor `and which closes the shutoff valve after the motor has completed a requisite number of revolutions so that the valve prevents further flow of compressed gas to and thereby arrests the motor.

The novel features which are considered as characteristic of the invention are set forth in particular in the `appended claims. The improved rotary impact tool itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawings, in which:

FIG. l is a fragmentary axial section through the rear portion of a rotary impact tool which embodies one form of our invention and wherein the shutoff valve is shown in a position in which the motor is connected with a source of compressed air;

FIG. 2 is a fragmentary detail View of a transmission forming part of the counter mechanism which is utilized in the impact tool of FIG. 1;

FIG. 3 illustrates the structure of FIG. 1 with the shutoff valve in a different position in which the flow of compressed air to the motor is interrupted; and

FIG. 4 is a partly elevational and partly sectional view of the impact tool which embodies the structure of FIG. 1.

Referring to FIG. 1, there is shown a porti-on of a pontable pneumatically operated rotary impact Ytool which may be used as a wrench for installing or removing bolts and nuts, as a screwdriver, and for similar purposes. The .tool comprises an elongated 'housing l1 having at its rear end a handgrip portion 1a provided w-ith an air inlet 2 to receive the discharge end of an air -h-ose 2 which is connected to the pressure side of a compressor or another source of compressed air, not shown. The handgrip portion 1a lis provided `with a .supply channel 3 discharging into an annular space 7 of a regulator valve 4 which serves -to control the flow of compressed air to an arresting device here shown as a shutoff valve 10 as well as .to reset the novel counter mechanism of the impact tool. The valve 4 comprises an elongated valve stem -5 which `is reciprocable in a bore provided in the front pant of the handgrip portion 1a an-d -which is biased upwardly, as viewed in \FIG. 1, :by a helical return spring 6 so .that `the rounded head of the valve imemiber 5 abuts against a manually operable actuating member here shown as a trigger 4a which is pivoted to :the handgrip portion 1a and which may be depressed by the thumb .of that hand whose fingers extend through a cutout A1b of the hous-ing 1. )In iFlG. l, the trigger 4a has depressed :the valve member 5 against the bias of the spring 6 so that air entering the annular space 7 imay flow through a c-onnecting channel 8 and through a further channel 9 into an annular space `10a of the shutoff valve 1li. This valve is open and permits air to iiow int-o -a feed channel 17 which leads to the intake of a reversible pneumatic motor 21. The exact construction of the motor 21 -f-orms no part of this invention, and it suiices to say there that the motor serves to rotate an anvil 45 (see FIG. 4) which in turn rotates a wrench, a screwdriver or the like coming in direct engagement with a bolt, nut or screw. The motor 21 also -drives a rotary member here shown as a worm shaft 22 (see also FIG. 2) which is in mesh with a worm wheel 23. The worm shaft 22 .and worm wheel 23 constitute the transmission of an adjustable counter mechanism serving to determine the number of revolutions which the motor 21 can perform before the shutoft valve 1t) seals the channel 9 `from the channel 17 to terminate the tiow of compressed air to the motor. For example, the motor 21 may be of the type disclosed in U.S. Letters Patent No. 3,068,973 to Maurer.

The worm wheel 23 carries two [pivot pins y2.4 each of which supports one lof two jaws 25, 215 and these jaws together constitute a two-piece chuck for a re-ciprocable control member here shown as a spindle `29. The lettthand end portions of the jaws 25, 25' are provided with internal threads 42 to mate with external lthreads on the larger-diameter median portion of .the control spindle 29. An annular resilient element 26 surrounds the jaws 25, 25' and biases them into mesh with the control spindle 29. InL other words, the resilient element 26 tends to rock the lower jaw 25 about the corresponding pivot pin 24 and in a clockwise direction, las viewed in FIG. l, and at the same time tends to rock the jaw -25 in a counterclockwise direction. The right-hand end portion `28 of the contro-l spindle 29 is of non-circular cross sect-ion and is received in a complementary non-circular bore 35 of the housing 1 so that the control spindle is held against rotation. Consequently, and as soon as the motor `2&1 begins to rotate in a sense to apply a nut, a bolt or the like, .the worm sha-ft 22 rotates the worm wheel 23 and the latter rotates the ja-ws 25, 25 so that the control spindle .29 moves lin a direction to the right, as viewed in FlG. l, and engages a lprojection 36 provided at one axial end of a reciprocable piston-like valve member 37 in the control valve 10. The arrangement .i-s such :that the worm wheel 23 completes a predeterm-ined number of revolu- .tions before the non-circular end portion 28 of the spin- -dle 29 reaches an-d Ibegins .to shift the projection 36. The control valve 10 comprises a valve spring 13 which operates between a xed cap and the valve member y37 and tends to maintain `the valve member 37 in .an end position of abutment with a valve seat 19 defined by the casing of the valve `1th and surrounding a small compartment 111 so that this compartment is normally sealed trom a branch line -or channel 18 which communicates with the channels 8 and 9. The compartment 1=1 is vented through a bore `16 in the valve member 37, through a space 12 -between the valve member 37 and cap 15, and through a port 14 provided in the end wall of Vthe cap 15. When the end portion 28 of the control `spindle 29 begins .to move the projection 36 in a direct-ion to .the right, as viewed in -FIG. l, the head of the valve member 37 moves away from the annular seat 19 and permits compressed air to flow from the channel 1S into the comparl ment 1-1. The pressure in the compartment `1'1 `rises very rapidly because the diameter of the bore 216 is small so that the valve member 37 is shifted rapidly against the bias of .the spring `13 and assumes a second end position tin which its -head seals the channel 9 from the channel 17 `to arrest the motor 211. In other words, the motor `21 is arrested in a fully automatic way as soon as the worm shaft 22 completes a predetermined number of revoludi? tions, and this number may be selected by an adjusting screw 31 iwhich is threaded into a plunger t41 provided in a bore of the housing 1 which also accommodates the jaws 25, 25'. The plunger 41 acts not unlike a wedge and :serves to move the jaws 215, 25 apart against the bias yol? the resilient element 26 so that a spring 27 may return the control spindle 29 to its left-hand end position in which a tip `31B of the spindle abuts against the adjusting screw 31. The plunger 41 may be shifted by compressed air when, after having noted that the motor 21 is arrested, the operator releases the trigger 4a so that .the return spring 6 may move the valve member 5 to its upper end position which is shown in lPEG. 3. The channel 3 is then se-aled from. the channel 8 .but is tree to communicate with a bypass channel y34 via a bore 39 provided in the valve member 5. The channel 34 dclivers a stream of compressed -air into a chamber I32 at the ett-hand end tace of the plunger 411 so that the conical tip 43 of this plunger penetrates between the suitably inclined end tfaces of the jaws l25, 25 and spreads the jaws against the bias of the resilient element 26 whereby the control yspindle 29 is tree to jump back (under the bias ot the spring 27) and its tip 30 returns in abutment twith the adjusting screw 31. The spring l13 then returns the head of the valve member 37 in abutment with the seat 19 so that the valve member 37 reestablishes the connection between the channels 9 and `17 and the motor 2X1 will be started as soon .as the operator decides to depress the trigger y4a. When the operator releases the trigger 4a, the channel S is -free to communicate with the atmosphere through a discharge port -3-8 of the regulator valve 4. The Volume of the annu-lar space 16a in the control valve 10 is reduced to Zero lwhen the channel 1,8 is free to communicate with the compartment `11 because the head of the valve member 37 then abuts against the end tace of the cap 15. AThis compartment 1v1 continues to communicate with the atmosphere through ythe bore 16, space 12 and port 14.

The bore through which the operator may gain access to the adjusting screw 31 lis normally sealed by a screw plug 33 which seals the chamber 32 at the left-hand end face of the plunger 41 from the atmosphere. When the trigger 4a is depressed, the bypass channel 34 is free to communicate with the discharge port 38 through an annular space 4t) in the regulator valve 4 so that the pressure in the chamber 32 equals atmospheric pressure and the resilient element 26 is free to move the jaws 25, 25 toward each other and into mesh with the externally threaded median portion of the control spindle 29.

It will be noted that, in order to select the number of revolutions which the impact tool should perform before the motor 21 is brought to a halt, the operator must remove the plug 33 and then adjusts the screw 31 by means of a screwdriver in order to select the initial distance between the end portion 28 of the control spindle 29 and the projection 36 of the control valve member 37. The control spindle 29 is reset to its initial position in a fully automatic way as soon as the operator releases the trigger 4a of the regulator valve 4 and, in response to renewed depression of the trigger 4a, the motor 21 is started automatically to complete -a predetermined number of revolutions prior to being arrested by movement of the control valve member 37 to the end position of FIG. 3.

FIG. 4 illustrates on a smaller scale the front portion of the impact tool which includes an anvil 45 having a socket lock 46 which may be coupled to a wrench or the like, a hammer 47, a planetary gearing including a sun gear 22 which is coaxial with the worm shaft 22 and which is driven by the motor 21, planet pinions 48 which mesh with the sun gear 22 and with a ring gear 49, and a planet carrier 5t) for the pinions 48. The planet carrier 50 is coupled with the hammer 47 by means of balls 51 which are received in grooves 52, 52a and the hammer carries claws 53 which engage complementary claws 54 on the anvil 45. The hammer 47 is biased by a strong helical spring 55 so that the claws 53, 54 normally transmit torque but will be disengaged from each other when the anvil 45 meets a predetermined resistance to rotation. The exact construction `of the assembly shown in the lower part of FIG. 4 forms no part of the present invention which resides mainly in the provision of the adjustable counter mechanism serving to arrest the motor 21 after a predetermined number of revolutions. The grooves 52a are of helical shape so that the hammer 47 may travel upwardly, as viewed in FIG. 4 to disengage its claws 53 from the claws 54 of the anvil 45. The spring 55 then returns the hammer 47 to the position of FIG. 4 whereby the claws 53 reengage the claws 54 and impart to the anvil a strong impulse so that the anvil may lturn the socket lock 46 through a given angle in order to drive the nut or bolt home.

The pneumatic motor 21 may be replaced by an electric motor. In such impact tools, the arresting means comprises a normally closed switch connected in circuit with the motor and serving to open the circuit when the motor completes a predetermined number of revolutions. The counter mechanism then comprises a suitable control spindle lor the like which opens the switch as soon as the motor completes such predetermined number of revolutions.

Referring again to FIGS. 1 and 3, the impact tool of our invention is further provided with a signal generating device 60 which is secured to the housing 1 and which produces a readily perceptible signa-l when the shutoff valve has arrested the motor 21. In the illustrated embodiment, the signal generating device 60 is arranged to produce an audible signal and'preferably takes the form of a conventional horn, whistle, buzzer or the like. As shown in FIG. l, the compartment 11 communicates with a channel 61 which is sealed from the channel 18 when the head of the valve member 37 abu-ts against the seat 19. However, when the control spindle 29 causes the valve member 37 to take the position `of FIG. 3 in which the channel 8 is sealed from the feed channel 17, the channel 61 is free to communicate with the channel 18 and delivers to the device 60 a stream of compressed air which causes this device to produce an audible signal. Thus, if the operator fails to note that the motor 21 is arrested, he is warned by an audible signal produced by the device 60 and is induced to release the trigger 4a so that the regulator valve 4 admits air into the chamber 32 in order to permit the spring 27 to return the control spindle 29 to the position of FIG. 1. At the same time, the spring 13 returns the valve member 37 to the end position of FIG. 1 whereby the head of this valve member seals the channel 61 from the channel 18 to inactivate the signal generating device 60. In fact, the signal generating device 60 will be inactivated even before the control spindle 29 returns to the position of FIG. l because, by releasing the trigger 4a, the operator seals the channel 3 from the channel 8 so that the pressure in the compartment 11 drops immediately regardless of the axial position of the control spindle.

It goes without saying that the signal generating device may be arranged to produce a visible signal, for example, by providing it with a light bulb and a battery in circuit with a switch which completes the circuit in response to increased tluid pressure or in response to axial movement of the control spindle 29. All that counts is to provide a s-ignal generating device which is arranged to produce a visible or audible signal as soon as the motor 21 completes a requisite number of revolutions so that the operator is warned to release the trigger 4a and is apprised of the fact that the impact tool has completed the application or removal of a screw, bolt, nut or the like. It is further evident that the channel 61 which leads to the signal generating device 60 may be connected with the source of compressed lluid in direct response to changes in axial position of the control spindle 29 without in any way departing from the spirit of our invention.

A very important advantage of our improved impact tool is that the motor is arrested after 1a predetermined number of revolutions. This is of utmost importance when a large number of bolts or nuts must be installed with equal force to make sure that each bolt or nut will take up an equal share of stresses. In many conventional impact tools in which the motor is arrested by a time lag relay or the like after elapse of a predetermined interval of time, the number of rotations performed during such intervals often uctuates Within wide limits be-l cause the operation of the relay depends oniluctuations in the ow of electric current and because the number of revolutions per unit of time often depends on the resistance which a screw, nut or bolt offers to rotation as well as on fluctuations in the flow of electric current or a pressure fluid which is used to rotate the motor. Our improved rotary impact tool is entirely independent of such factors because the counter mechanism counts the number of revolutions which the motor actually performs, not the length of time during which the motor remains in operation or the resistance which the anvil encounters during such rotation. Since the counter mechanism may be adjusted in a very simple way, the impact tool of our invention may be put to use under widely dierent circumstances wherever one or more bolts, screws or nuts must be installed or removed with a given force. The total driving torque which is transmitted to the anvil is always the same if the motor is permitted to perform a given number of revolutions -because such given number of revolutions is counted independently of the time which elapses while the motor 21 rotates to complete -say 100 revolutions and independently of the resistance which the motor encounters while it remains connected with the source of electric current or compressed Huid. Since the number of revolutions is directly related to the number of impacts which the anvil transmits to a screw, bolt or nut, the counter mechanism of our invention can be said to count the number of impacts by counting the number of revolutions.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of this invention and, therefore, such adaptations lshould and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a rotary impact tool, in combination, a rotary motor; arresting means movable between an initial nonarresting position and a second arresting position in which said motor is arrested; means operatively connected with said motor and arranged to move said arresting means from said initial non-arresting position to said second arresting position in response to said motor completing a predetermined number of revolutions; and means operative to shift said arresting means back from `said second arresting to said initial non-arresting position thereof independently of rotation of said motor so that Vsaid arresting means are in said initial position thereof preparatory to starting the next operation of the tool.

2. In a rotary impact tool, in combination, a rotary pneumatic motor; a channell for conveying a compressed gas to said motor; normally open shutoff valve means provided in said channel and movable between an initial open position permitting flow of compressed Ygas to said lmotor and a shut position preventing the ow of compressed gas to said motor; and counter means comprising a rotary member driven by said motor and arranged to operate said shutoff valve means to move the same from said open to said shut position thereof and to thereby 'Z arrest said motor after said rotary member completes a predetermined number of revolutions; and means operative to shift said valve means back to said initial open position thereof independently of rotation of said motor.

3. In a rotary impact tool, in combination, a rotary pneumatic motor; a housing receiving said motor and having channel means for conveying a compressed fiuid thereto; arresting means 4including a shutoff valve provided in said channel means and comprising a movable valve me-mber normally occupying one of two positions in the other of which said valve prevents the ow of compressed uid to said motor; and counter means located within said housing comprising a control member received in said housing and normally occupying the first of two positions in the second of which said control mem* ber moves said valve member to said otherposition, and transmission means operatively connected with said motor and arranged to move said control member to said second position when the motor completes a predetermined number of revolutions so that said shutoff valve arrests the motor.

4. In a portable rotary impact tool, in combination, a rotary pneumatic motor; a housing receiving `said motor and having channel means for conveying a compressed fluid thereto; arresting means including a shutoff valve provided in said channel means and comprising7 a movable valve member normally occupying one of two positions in the other of which said valve prevents the liovv of compressed fiuid to said motor; counter means comprising a control member received in said housing and normally occupying the first of two positions in the second of which said control member moves said valve member to said other position, and transmission means operatively connected with said motor and arranged to move said control member to said second positon when the motor completes a predetermined number of revolutions so that said shutoff valve arrests the motor; and adjusting means for deter-mining the first position of said control member and for thereby selecting the number of revolutions which the motor completes prior to being arrested by said valve member.

5. In a rotary impact tool, in combination, a rotary pneumatic motor; a housing receiving said motor and having channel means for conveying a compressed uid thereto; arresting means -including a shutoff valve provided in said channel means and comprising a -movable valve member normally occupying `one of two positions in the other of which said shutoff valve prevents the ow of compressed uid to said motor; and counter means located within said housing and comprising .a control spindle reciprocably received in said housing and normally occupying the first of two positions in the second of which said spindle moves said valve member to said other position to arrest the motor, and transmission means driven by said motor and arranged to move said spindle from said first to said second position after the motor com-pletes a predetermined number of revolutions so that said shutoff valve then arrests said motor.

6. In a rotary impact tool, in combination, a rotary pneumatic motor; a housing receiving said motor and having channel means for conveying a compressed uid there-to; arresting means including a shutoff valve provided in said channel means and comprising a movable valve member normally occupying one of two positions in the other of which said shutoff valve .prevents the flow of compressed uid to said motor; counter means comprising a control spindle reciprocably received in said housing and normally occupying the first of two positions in the second of which said spindle moves said valve member to said other position to arrest the motor, and transmission -means driven \by said motor and arranged to move said spindle from said first to said second position while the mo-tor completes a -predetermined number of revolutions so that said shutoff valve then arrests said motor; and a normally closed regulator valve provided in said channel means ahead of said shutoff valve and comprising manually operated trigger means to open the same at the will of the operator so that compressed uid is free to flo-w to said shutoff valve.

7. A lcombination -as set forth in claim 6, wherein said spindle comprises a threaded portion and further comprising means for returning said spindle to said first position thereof including a pair of jaws having threaded portions arranged to mesh with the threaded portion of said spindle, means connecting said jaws for rotation with said transmission means, resilient means for biasing said jaws into mesh with said spindle so that the spindle is moved to said second position in response to rotation of said jaws when said motor rotates, spring means for biasing said spindle to said first position thereof, and pneumatically operated means for disengaging said spindle from said jaws against the .bias of said resilient means.

8. A combination as set forth in claim 7, wherein said pneumatically operated means comprises a plunger having inclined faces cooperating with inclined faces provided on said ja-ws, and bypass channel means provided in said housing and extending to said regulator valve to convey a stream of compressed iiuid against said plunger when said regulator valve is closed so that the plunger spreads said jaws and permits the spring means -to ret-urn said spindle to said rst position thereof.

9. A combination as set forth in claim 6, wherein said transmission means comprises a worm shaft driven .by said motor and a worm wheel meshing with said Worm shaft, said counter means further comprising members driven by said worm wheel and normally in motion transmitting engagement with said spindle to shift the spindle axially to said second position thereof in response to rotation of said motor.

d0. A combination as set forth in claim 6, further comprising means for holding said spindle against rotation in said housing.

illl. A combination as set forth in claim 6, further comprising a signal genera-ting device responsive to movement of said valve memtber to said other position thereof to produce a signal indicating to the operator that the trigger means of said regulator valve may be released.

12. A combination as set Iforth in claim. 6, further comprising adjusting means for selecting the first position of said spindle, said adjusting means comprising a threaded member axially movably mounted in said housing and arranged to determine vthe length of tra-vel of said spindle from the second to the first position thereof.

References .Cited by the Examiner UNITED STATES PATENTS 453,247 6/1891 Smith 91-1 976,727 ll/ 1910 Crump 91--1 1,540,870 6/1925 Adams 91-1 2,373,621 4/1945 Wales 91-1 .2,709,062 5/1955 ALamb 91--2 2,743,897 5/1956 Elliott et al. 91-2 SAMUEL LEVINE, Primary Examiner.

P. E. MASLOUSKY, Assistant Examiner. 

1. IN A ROTARY IMPACT TOOL, IN COMBINATION, A ROTARY MOTOR; ARRESTING MEANS MOVABLE BETWEEN AN INITIAL NONARRESTING POSITION AND A SECOND ARRESTING OPOSITION IN WHICH SAID MOTOR IS ARRESTED; MEANS OPERATIVELY CONNECTED WITH SAID MOTOR AND ARRANGED TO MOVE SAID ARRESTING MEANS FROM SAID INITIAL NON-ARRESTING POSITION TO SAID SECOND ARRESTING POSITION IN RESPONSE TO SAID MOTOR COMPLETING A PREDETERMINED NUMBER OF REVOLUTIONS; AND MEANS OPERATIVE TO SHIFT AND ARRESTING MEANS BACK FROM SAID SECOND ARRESTING TO SAID INITIAL NON-ARRESTIONG POSITION THEREOF INDEPEDENTLY OF ROTATION OF SAID MOTOR SO THAT SAID ARRESTING MEANS ARE IN SAID INITIAL POSITION THEREOF PREPARATORY TO STARTING THE NEXT OPERATION OF THE TOOL. 